How to correctly handle unequal floating point decimals in PHP

When comparing floating point numbers in PHP, unequal floating point numbers may occur. This is caused by the storage precision of floating point numbers. To handle this situation correctly, there are a few things you can do to avoid unequal results.

1. Use comparison functions

In PHP, you can use comparison functions to determine whether two floating point numbers are equal. PHP provides a float_cmp function that can be used to compare whether two floating point numbers are equal. The sample code is as follows:

function float_cmp($a, $b, $epsilon = 0.00001) {
    return abs($a - $b) < $epsilon;
}

$a = 0.1 + 0.2;
$b = 0.3;

if (float_cmp($a, $b)) {
    echo "两个浮点数相等";
} else {
    echo "两个浮点数不相等";
}

In the above example, by defining the float_cmp function to compare whether two floating point numbers are equal, by setting a small error rangeepsilonTo determine whether their difference is within the tolerable range, thereby avoiding the storage accuracy problem of floating point numbers.

2. Use integer operations instead of floating-point operations

Another way to avoid floating-point inequality is to use integer operations instead of floating-point operations. You can convert floating point numbers to integers for operation, and finally convert the results back to floating point numbers. This can avoid problems caused by the storage precision of floating point numbers.

The sample code is as follows:

$a = 0.1 * 10 + 0.2 * 10;
$b = 0.3 * 10;

if ($a == $b) {
    echo "两个浮点数相等";
} else {
    echo "两个浮点数不相等";
}

In the above example, the floating point number is multiplied by an appropriate multiple and converted into an integer for operation, and the comparison results are equal, thus avoiding the need for floating point number storage precision. question.

Summary:

When dealing with unequal floating point numbers in PHP, you can avoid problems by using comparison functions or integer operations instead of floating point operations. At the same time, when comparing floating point numbers, pay attention to setting a reasonable error range to determine whether they are equal to avoid being affected by the storage accuracy of floating point numbers. Mastering the correct processing method can effectively avoid the problem of unequal floating point numbers and improve the accuracy and stability of the program.

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